As known, the applications of shafts are very wide. For example, a transmission shaft of an automatic document feeder, a transmission shaft of an ejecting mechanism of a post-processing device, a transmission shaft of a feeding mechanism of a paper shredder and a pivotal shaft between an upper cover and a base of an electronic device are some kinds of widely-used shafts. The shaft is usually used for transferring kinetic energy to drive rotation or movement of other components. Alternatively, two components may be connected with each other via the shaft, so that these two components may be rotated relative to each other. Generally, the shaft is installed in the region between two supporting parts, and two position-limiting elements are respectively located at both ends of the shaft for preventing detachment of the shaft.
The conventional position-limiting element is for example a C-shaped ring or an E-shaped ring. Hereinafter, a conventional shaft positioning device will be illustrated by referring the E-shaped ring as the position-limiting element. FIG. 1 is a schematic exploded view illustrating a conventional shaft positioning device. As shown in FIG. 1, the shaft positioning device 1 comprises a base 10, a first supporting part 11, a shaft 12, and a position-limiting element 13. The first supporting part 11 comprises a first hole 11a. The shaft 12 comprises a first ring-shaped recess 121. The position-limiting element 13 is an E-shaped ring.
It is noted that only at a first side of the base 10 and a first end of the shaft 12 are shown in FIG. 1. However, a second supporting part (e.g. a second hole) with the same structure as the first supporting part 11 is located at a second side of the base 10, and a second ring-shaped recess with the same structure as the first ring-shaped recess 121 is located at a second end of the shaft 12. For clarification and brevity, the second supporting part and the second ring-shaped recess are not shown in FIG. 1. Similarly, the shaft positioning device 1 has an additional position-limiting element (not shown) corresponding to the second end of the shaft 12.
FIG. 2 is a schematic assembled view illustrating the conventional shaft positioning device of FIG. 1. Hereinafter, a sequence of assembling the conventional shaft positioning device 1 will be illustrated with reference to FIGS. 1 and 2. Firstly, the two ends of the shaft 12 are penetrated through the first hole 11a and the second hole, respectively. Then, the two position-limiting elements 13 are engaged with the first ring-shaped recess 121 and the second ring-shaped recess, respectively.
After the two position-limiting elements 13 are respectively engaged with the first ring-shaped recess 121 and the second ring-shaped recess, if the shaft 12 is moved in a left direction or a in a right direction, a corresponding position-limiting element 13 is contacted with the first supporting part 11 or the second supporting part. Since both of the two ends of the shaft 12 fail to be detached from the first hole 11a and the second hole, the shaft 12 is positioned between the first supporting part 11 and the second supporting part.
From the above discussions, the two position-limiting elements 13 of the conventional shaft positioning device 1 are respectively located at the two ends of the shaft 12 in order to fix the shaft 12 between the first supporting part 11 and the second supporting part.
Hereinafter, an installation tool for installing the C-shaped ring or the E-shaped ring will be illustrated with reference to FIG. 3. FIG. 3 is a schematic perspective view illustrating an installation tool for installing the position-limiting element.
As shown in FIG. 3, the installation tool 14 comprises two clamping pieces 15, a rivet 16, a compression spring 17, and two clamping legs 18. Moreover, the two clamping legs 18 have respective tapered posts 181 at the top sides thereof.
The two clamping pieces 15 are crisscrossed. In addition, the two clamping pieces 15 are combined together through the rivet 16. A first end of each of the two clamping pieces 15 is formed as a handle 151. A second end of each of the two clamping pieces 15 is formed as the clamping leg 18. The installation tool 14 further comprises a receiving slot 19. The receiving slot 19 runs through the two clamping pieces 15 and located under the rivet 16. The compression spring 17 is accommodated within the receiving slot 19. After the two clamping pieces 15 are moved toward each other, the two clamping pieces 15 may be returned to the original positions by means of the compression spring 17.
Hereinafter, the operations of the installation tool 14 will be illustrated with reference to FIGS. 1 and 3. A process of installing the position-limiting element 13 by the installation tool 14 will be illustrated as follows. Firstly, the two tapered posts 181 are inserted into the inner periphery of the position-limiting element 13 to prop the position-limiting element 13 open. Then, the installation tool 14 is moved to the position near the shaft 12, and the position-limiting element 13 is aligned with the first ring-shaped recess 121. Then, the two handles 151 are gripped to allow the two clamping legs 18 to be moved toward each other. Consequently, the position-limiting element 13 is restored to the original shape and inserted into the first ring-shaped recess 121.
However, the conventional shaft positioning device still has some drawbacks. For example, since the shaft positioning device is only able to position the shaft having ring-shaped recesses at the both ends thereof, the process of fabricating the shaft positioning device is inconvenient and the fabricating cost is high. Moreover, the use of the installation tool to install the C-shaped ring or the E-shaped ring needs a large installation space. In other words, it is necessary to reserve large installation spaces beside the two supporting parts. Under this circumstance, the overall volume of the shaft positioning device is increased. The increased volume is detrimental to the general trends in designing light and small products.
Therefore, there is a need of providing an improved shaft positioning device in order to eliminate the above drawbacks.